The present invention relates to a hydraulic brake system with anti-lock control, in particular for automotive vehicles.
A brake system of this type has been described in German patent application P 39 34 624. This system is known as a "closed-loop" ABS-system wherein, in contrast to the known "open-center" ABS-system, the auxiliary-pressure and return delivery system is not in direct communication with the unpressurized supply reservoir arranged on the master cylinder side. During the brake slip control action, the auxiliary-pressure system takes necessary pressure fluid volume from the low-pressure accumulator arranged on the return line to the pump and supplies this fluid to the main pressure line. Excess pressure fluid is, at the same time, delivered to a high-pressure accumulator arranged in the branch line to the auxiliary-pressure line and comprising a stepped piston, the extension of this accumulator cooperating with a valve member for the purpose of uncoupling the master cylinder from the connected wheel brake. The anti-lock control will then be effected in the associated wheel brakes in dependence on the electromagnetic actuation of the inlet valves and outlet valves interposed in the main pressure line and the return line, while the master cylinder is isolated from the controlled wheel brakes by the valve member closing the main pressure line.
Due to this structure, this brake system cannot be of compact design and cannot perform a braking pressure control action without the electromagnetic inlet valves necessary in the main pressure lines.